In the related art, an image forming apparatus or a paper feeding apparatus is provided with a mechanism for detecting the size of a paper stacked in a paper cassette. With the enhancement of functionality of the image forming apparatus, the image forming apparatus becomes complicated and has a lot of members. In terms of user's convenience, it is undesirable that the image forming apparatus is increased in height in a height direction. Therefore, it is necessary to reduce the height of the paper cassette in the paper feeding apparatus disposed at a lower end of the image forming apparatus.
With the enhancement of functionality of the image forming apparatus, in order to suppress an error when printing, it is necessary to accurately detect the size of the paper stacked in the paper cassette.
The paper cassette has a sidewall and an end wall that are movable along a width direction of the stacked paper and a longitudinal direction of the paper cassette. Two paper size sensors for detecting the size of the paper stacked in the paper cassette when the paper cassette is inserted into the paper feeding apparatus are provided at a position opposed to the paper cassette on the depth side of the paper feeding apparatus. Each of the paper size sensors detects the size in the paper width direction or the longitudinal direction of the paper cassette by combinations of presses. A control unit detects the paper size on the basis of a combination of the sizes in the paper width direction and the longitudinal direction of the paper cassette detected by the two paper size sensors.
The paper cassette is provided with a movable member that is movable in accordance with the movement of the sidewall, and a movable member that is movable in accordance with the movement of the end wall. The movable members correspondingly press the paper size sensors. At this time, the movable member connected to the sidewall and the movable member connected to the end wall are disposed in the paper cassette with the same rotation fulcrum.
FIGS. 47 and 48 show a related art example of a first movable member 205 and a second movable member 206 provided in a cassette main body 201. FIG. 47 is a diagram of a paper cassette 201 when viewed from its rear surface in a state where the paper cassette 201 is inserted into an image forming apparatus 1. FIG. 48 is a diagram of a first sensor 102 and a second sensor 103 when viewed from the depth side of the image forming apparatus 1.
As shown in FIG. 47, the first movable member 205 and the second movable member 206 are disposed on the rear surface of the cassette main body 201 on the same axis. Therefore, as shown in FIG. 48, the first sensor 102 and the second sensor 103 are arranged in the height direction on the same axis of the paper feeding apparatus 20 or the image forming apparatus 1. For this reason, the paper cassette 201 cannot be decreased in height (JP-A-2005-280994).
When the printing position of an image is misaligned with respect to the paper width direction, it is necessary to shift the paper position in the paper cassette so as to be aligned with the image to be printed (hereinafter, referred to as lateral misalignment correction). When a user executes lateral misalignment correction of a paper, the sidewall is also moved. For this reason, the paper size sensors may detect a size different from a paper size desired to be actually detected or may not specify any size. For this reason, when the user executes the lateral misalignment correction of the paper in the paper cassette, it is also necessary to move the paper size sensors, which leads to complexity.
Instead of the lateral misalignment correction of the paper, a method of correcting the position of an image when printing may be used. In this case, however, it is necessary to set a printable region in the image forming apparatus by an amount corresponding to the amount of lateral misalignment correction. For this reason, the image forming apparatus is increased in size, and manufacturing costs become high. In addition, according to this method, the position of the paper in the paper cassette is not corrected, and accordingly the paper is conveyed into the apparatus at a position different from a normal position. Then, the paper may collide against an unexpected place, and paper jam or bending may occur. When a lateral misalignment adjustment mechanism for the lateral misalignment correction is provided, it is necessary for the user to adjust the paper size sensors.
Accordingly, aspects of the invention provide a paper feeding apparatus that is capable of accurately detecting the size of a paper stacked in a paper cassette without increasing the size of the apparatus.